diff --git a/gtk2_ardour/midi_time_axis.cc b/gtk2_ardour/midi_time_axis.cc
index a8fc9c3e60..3da5f11f10 100644
--- a/gtk2_ardour/midi_time_axis.cc
+++ b/gtk2_ardour/midi_time_axis.cc
@@ -19,8 +19,6 @@
 #include <cstdlib>
 #include <cmath>
 
-#include <strings.h> // for ffs(3)
-
 #include <algorithm>
 #include <string>
 #include <vector>
@@ -28,6 +26,7 @@
 #include <sigc++/bind.h>
 
 #include "pbd/error.h"
+#include "pbd/ffs.h"
 #include "pbd/stl_delete.h"
 #include "pbd/whitespace.h"
 #include "pbd/basename.h"
@@ -1491,7 +1490,7 @@ MidiTimeAxisView::playback_channel_mode_changed ()
 		_playback_channel_status.set_markup (string_compose ("<b>%1</b>: <i>%2</i>", _("Play"), _("some")));
 		break;
 	case ForceChannel:
-		_playback_channel_status.set_markup (string_compose ("<b>%1</b>: <i>%2>%3</i>", _("Play"), _("all"), ffs (midi_track()->get_playback_channel_mask())));
+		_playback_channel_status.set_markup (string_compose ("<b>%1</b>: <i>%2>%3</i>", _("Play"), _("all"), PBD::ffs (midi_track()->get_playback_channel_mask())));
 		break;
 	}
 }
@@ -1507,7 +1506,7 @@ MidiTimeAxisView::capture_channel_mode_changed ()
 		_capture_channel_status.set_markup (string_compose ("<b>%1</b>: <i>%2</i>", _("Rec"), _("some")));
 		break;
 	case ForceChannel:
-		_capture_channel_status.set_markup (string_compose ("<b>%1</b>: <i>%2>%3</i>", _("Rec"), _("all"), ffs (midi_track()->get_capture_channel_mask())));
+		_capture_channel_status.set_markup (string_compose ("<b>%1</b>: <i>%2>%3</i>", _("Rec"), _("all"), PBD::ffs (midi_track()->get_capture_channel_mask())));
 		break;
 	}
 }
diff --git a/libs/ardour/ardour/midi_track.h b/libs/ardour/ardour/midi_track.h
index 3b75c0a51b..9c1d21a3e4 100644
--- a/libs/ardour/ardour/midi_track.h
+++ b/libs/ardour/ardour/midi_track.h
@@ -20,6 +20,8 @@
 #ifndef __ardour_midi_track_h__
 #define __ardour_midi_track_h__
 
+#include "pbd/ffs.h"
+
 #include "ardour/track.h"
 #include "ardour/midi_ring_buffer.h"
 
@@ -183,7 +185,7 @@ private:
 /* if mode is ForceChannel, force mask to the lowest set channel or 1 if no
  * channels are set.
  */
-#define force_mask(mode,mask) (((mode) == ForceChannel) ? (((mask) ? (1<<(ffs((mask))-1)) : 1)) : mask)
+#define force_mask(mode,mask) (((mode) == ForceChannel) ? (((mask) ? (1<<(PBD::ffs((mask))-1)) : 1)) : mask)
 
 	void _set_playback_channel_mode(ChannelMode mode, uint16_t mask) {
 		mask = force_mask (mode, mask);
diff --git a/libs/ardour/midi_diskstream.cc b/libs/ardour/midi_diskstream.cc
index a21f3fb6f4..d27c2fa9c7 100644
--- a/libs/ardour/midi_diskstream.cc
+++ b/libs/ardour/midi_diskstream.cc
@@ -26,10 +26,10 @@
 #include <fcntl.h>
 #include <cstdlib>
 #include <ctime>
-#include <strings.h> // for ffs(3)
 #include <sys/stat.h>
 
 #include "pbd/error.h"
+#include "pbd/ffs.h"
 #include "pbd/basename.h"
 #include <glibmm/threads.h>
 #include "pbd/xml++.h"
@@ -438,7 +438,7 @@ MidiDiskstream::process (BufferSet& bufs, framepos_t transport_frame, pframes_t
 				break;
 			case ForceChannel:
 				if (ev.is_channel_event()) {
-					ev.set_channel (ffs(mask) - 1);
+					ev.set_channel (PBD::ffs(mask) - 1);
 				}
 				_capture_buf->write(transport_frame + loop_offset + ev.time(),
 						    ev.type(), ev.size(), ev.buffer());
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index f7f9ff7a59..51edd06aee 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -17,8 +17,7 @@
     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
-#include <strings.h> // for ffs(3)
-
+#include "pbd/ffs.h"
 #include "pbd/enumwriter.h"
 #include "pbd/convert.h"
 #include "evoral/midi_util.h"
@@ -504,7 +503,7 @@ MidiTrack::filter_channels (BufferSet& bufs, ChannelMode mode, uint32_t mask)
 				}
 				break;
 			case ForceChannel:
-				ev.set_channel (ffs (mask) - 1);
+				ev.set_channel (PBD::ffs (mask) - 1);
 				++e;
 				break;
 			case AllChannels: